(Corrects last paragraph to make it 16 million hectares instead of 16 hectares.)

By Ana Mano

SAO PAULO, March 16 (Reuters) - U.S. agricultural biotech firm Monsanto Co plans to push ahead with its launch schedule for soy seeds genetically modified to resist dicamba weed killer in Brazil, despite a pending patent dispute related to an older version of the technology, two executives told Reuters.

Monsanto will launch the product after it obtains regulatory approvals for it in China and the European Union.

“We do not let the process of patent challenges slow down our plans,” said Scott Partridge, the company’s vice president of global strategy. He said Monsanto is on track to obtain all approvals ahead of the launch.

The company also needs a Brazilian patent for the new biotechnology, the executives said. Farm trials are scheduled for the 2019/2020 crop season and the full commercial launch in 2021.

The Intacta2 Xtend product is engineered to resist weed killers containing dicamba, building on resistances to glyphosate and certain species of parasitic Spodoptera caterpillars featured in the older version, Intacta RR2 Pro.

But a looming patent battle could signal a repeat of troubles encountered in the launch of that previous-generation product.

Last year, a group of Brazilian farmers asked a federal court to cancel Monsanto’s Intacta RR2 Pro patent rights on the basis that it made no real technological innovation. The patent office told the court that, after re-examining the issue, the patent should be declared void.

Maria Luiza Nachreiner, who heads Monsanto’s soy business in South America, said the company “is confident” the courts will uphold its intellectual property rights, adding that a formal challenge to the patent office opinion will be filed this month.

Intacta RR2 Pro’s patent protection currently extends through October 2022.

Monsanto is no stranger to legal battles.

By 2013, it had stopped collecting royalties linked to its first-generation Roundup Ready soy seed technology after farmers claimed in Brazilian court that the patent had expired.

Monsanto settled the issue by giving some farmers a discount if they switched to the then-new Intacta RR2 Pro seed.

Partridge declined to speculate on the outcome of the pending Intacta-related patent dispute. He said that significant time and costs go into bringing a new trait to market and defended “a method to achieve a recovery of that cost.”

In the fields, Monsanto expects Brazilian farmers to adopt the new seed as quickly as their counterparts in the United States.

Monsanto estimates that in the United States about 40 million acres (16 million hectares) will be planted with dicamba-resistant soy seeds in 2018, twice as much as last year. (Reporting by Ana Mano, Editing by Rosalba O’Brien and Jonathan Oatis)